Cardinality of inputs & outputs

We currently say:

   On compound steps and p:declare-step, an input declaration can
   indicate if a sequence of documents is allowed to appear on the port.
   If sequence is specified with the value “yes”, then a sequence is
   allowed. If sequence is not specified on p:input, or has the value
   “no”, then it is a dynamic error (err:XD0006) for a sequence of more
   than one document to appear on the declared port.

Does that mean that given:

   <p:input port="preprocess" sequence="no" />

I can bind the preprocess input port to zero documents?

I wonder whether we should have the capability to constrain ports to say 
they expect/produce zero-or-one, exactly-one, zero-or-more and one-or-more.

If we don't, I think we need a note or something just to make explicit 
that input ports with sequence="no" can accept zero documents.

Cheers,

Jeni
-- 
Jeni Tennison
http://www.jenitennison.com

Received on Tuesday, 22 May 2007 19:10:07 UTC